sink {base}R Documentation

Send R Output to a File

Description

sink diverts R output to a connection.

sink.number() reports how many diversions are in use.

sink.number(type = "message") reports the number of the connection currently being used for error messages.

Usage

sink(file = NULL, append = FALSE, type = c("output", "message"),
     split = FALSE)

sink.number(type = c("output", "message"))

Arguments

file

a writable connection or a character string naming the file to write to, or NULL to stop sink-ing.

append

logical. If TRUE, output will be appended to file; otherwise, it will overwrite the contents of file.

type

character. Either the output stream or the messages stream.

split

logical: if TRUE, output will be sent to the new sink and to the current output stream, like the Unix program tee.

Details

sink diverts R output to a connection. If file is a character string, a file connection with that name will be established for the duration of the diversion.

Normal R output (to connection stdout) is diverted by the default type = "output". Only prompts and (most) messages continue to appear on the console. Messages sent to stderr() (including those from message, warning and stop) can be diverted by sink(type = "message") (see below).

sink() or sink(file = NULL) ends the last diversion (of the specified type). There is a stack of diversions for normal output, so output reverts to the previous diversion (if there was one). The stack is of up to 21 connections (20 diversions).

If file is a connection it will be opened if necessary (in "wt" mode) and closed once it is removed from the stack of diversions.

split = TRUE only splits R output (via Rvprintf) and the default output from writeLines: it does not split all output that might be sent to stdout().

Sink-ing the messages stream should be done only with great care. For that stream file must be an already open connection, and there is no stack of connections.

If file is a character string, the file will be opened using the current encoding. If you want a different encoding (e.g. to represent strings which have been stored in UTF-8), use a file connection — but some ways to produce R output will already have converted such strings to the current encoding.

Value

sink returns NULL.

For sink.number() the number (0, 1, 2, ...) of diversions of output in place.

For sink.number("message") the connection number used for messages, 2 if no diversion has been used.

Warning

Do not use a connection that is open for sink for any other purpose. The software will stop you closing one such inadvertently.

Do not sink the messages stream unless you understand the source code implementing it and hence the pitfalls.

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

Chambers, J. M. (1998) Programming with Data. A Guide to the S Language. Springer.

See Also

capture.output

Examples

sink("sink-examp.txt")
i <- 1:10
outer(i, i, "*")
sink()
unlink("sink-examp.txt")

## capture all the output to a file.
zz <- file("all.Rout", open = "wt")
sink(zz)
sink(zz, type = "message")
try(log("a"))
## back to the console
sink(type = "message")
sink()
file.show("all.Rout")

[Package base version 2.15.3 Index]